Unsporting scandium

Emsley, John

doi:10.1038/nchem.2090

Cited by 29 publications

(17 citation statements)

References 3 publications

(2 reference statements)

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“…Sc, which exclusively occur in the +3 oxidation state, lacks affinity to combine with the common ore-forming anions. Thus, Sc 3+ hardly concentrates through geological processes and rarely forms Sc-rich minerals (Das et al, 1971;Emsley, 2014). Rather, it occurs as a trace element in a number of hydroxide, silicate, fluoride, sulfate and phosphate minerals.…”

Section: Introductionmentioning

confidence: 99%

Petrology and geochemistry of scandium in New Caledonian Ni-Co laterites

Teitler

Cathelineau

Ulrich³

et al. 2019

Journal of Geochemical Exploration

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The growing demand for scandium (Sc), essential for several modern industrial applications, thrives the mining industry to develop alternative Sc sources. In such context, significant Sc concentrations (~100 ppm) were recently reported in several Ni-Co lateritic oxide ores developed after mafic-ultramafic rocks. This contribution examines the distribution of Sc in Ni-Co laterites from New Caledonia, the sixth largest Ni producer worldwide. Representative lateritic profiles were selected based on the protolith type and include dunite, harzburgite and lherzolite protoliths, wherein the Sc content, determined by the relative proportion of olivine and pyroxene, ranges from <5 ppm in dunite to >10 ppm in lherzolite. In Ni-Co laterites, dissolution and leaching of primary Mg-rich silicates leads to the residual enrichment of iron as ferric oxides/oxyhydroxides in the upper horizons. Downward remobilisation and trapping of Ni and Co lead to their local enrichment to economic concentrations, with maximum grades reached in the rocky saprolite and in the transition laterite horizons, respectively. In contrast, maximum Sc enrichment occurs in the yellow laterite horizon, where Sc-bearing goethite reaches about ten times the Sc content of the parent rock. Consequently, harzburgite-and lherzolite-derived yellow laterites yield maximum Sc concentrations up to 100 ppm, together with moderate Ni and Co concentrations. There, Sc is a potentially valuable by-product that could be successfully co-extracted along with Ni and Co through hydrometallurgical processing. In addition to peridotite-hosted laterites, hornblende-rich amphibolites yield elevated Sc up to 130 ppm. The saprolitisation of amphibolites leads to the formation of a goethite-gibbsitekaolinite mixture with Sc concentrations >200 ppm. There, goethite is the main Sc carrier with up to 800 ppm Sc. Therefore, despite their relatively limited volumes, amphibolite-derived saprolites may also represent attractive targets for Sc in New Caledonia.

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Section: Introductionmentioning

confidence: 99%

Petrology and geochemistry of scandium in New Caledonian Ni-Co laterites

Teitler

Cathelineau

Ulrich³

et al. 2019

Journal of Geochemical Exploration

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“…Often considered as part of the rare-earth elements, as both Sc and the lanthanides occur in a trivalent state, the chemical properties of Sc differ significantly from those of other rare-earth elements 1 . This unique chemistry is exploited in high performance alloys and solid oxide fuel cells, resulting in a growing demand for this element 2 . A better understanding of the coordination chemistry of Sc is a prerequisite to developing innovative Sc-based applications 3 .…”

Section: Introductionmentioning

confidence: 99%

Influence of crystallographic environment on scandium K-edge X-ray absorption near-edge structure spectra

Chassé

Juhin

Cabaret

et al. 2018

Phys. Chem. Chem. Phys.

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The absence of an extensive series of Sc K-edge X-ray absorption near-edge structure spectroscopy (XANES) reference spectra and the scarcity of direct structural data on Sc are major hurdles to develop our understanding of Sc chemistry. However, this first step is essential to develop new Sc-based applications and to better understand the formation of Sc deposits. Here, we present a detailed comparative study of Sc K-edge XANES spectra of three Sc-bearing compounds: a garnet (CaScSiO), an oxide (ScO) and a phosphate (ScPO·2HO). First-principles calculations have been performed to interpret the origin of the K pre-edge spectral features. We demonstrate the validity of our approach by reproducing satisfyingly the experimental spectra. The densities of states projected on the absorbing Sc atom and its first neighbours give the possibility to interpret the position and intensity of the pre-edge XANES features in terms of Sc local environment. The pre-edge features provide information on p-d mixing of the absorber orbitals giving clues on the centrosymmetry of the site and on the mixing of the empty 4p orbitals of the absorber with empty 3d orbitals of the neighbours via the empty p orbitals of the ligands. We also show that these features give a first estimate of the crystal-field splitting energy (ca. 1.5 eV), inaccessible using other spectroscopic methods. Comparisons with K-edge spectra of other 3d ions from the literature reveal the specificities of the Sc pre-edge, indicating that core-hole screening is weaker than for Ti-bearing compounds. This study provides a dataset of spectral signatures and a theoretical basis for their interpretation, a requirement for future studies on Sc chemical form in synthetic and natural systems.

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“…End-uses range from biomedical research to electronics, lasers and ceramics but the demand is driven by energy issues (Emsley, 2014). Scandium finds applications in Al-Sc superalloys, increasing tensile strength and improving weldability while maintaining light weight, an energy-saving factor in …”

Section: Introductionmentioning

confidence: 99%

Scandium speciation in a world-class lateritic deposit

Chassé¹,

Griffin²,

O’Reilly³

et al. 2016

Geochem. Persp. Let.

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aerospace and automotive industries. In solid oxide fuel cells, the addition of Sc to the electrolyte improves conductivity and lowers the operating temperature, extending fuel cell life.Despite a crustal abundance of ca. 22 ppm (Rudnick and Gao, 2014), comparable to common elements such as copper or lead, current Sc production is limited to 10 t to 15 t per year (U.S. Geological Survey, 2016). The large ratio of ionic radius to charge of Sc 3+ hinders the concentration of scandium during most geochemical processes (Samson and Chassé, 2016). A notable exception concerns lateritic deposits developed over ultramafic-mafic rocks where Sc concentrations up to 100 ppm make it a potential by-product (Aiglsperger et al., 2016;Maulana et al., 2016). Recently, lateritic deposits with Sc concentrations high enough to mine as a primary product have been reported in Eastern Australia (Jaireth et al., 2014). Among these, the Syerston-Flemington deposit contains about 1350 t of Sc at an average concentration of 434 ppm Sc (Pursell, 2016), providing a century-long resource at the present levels of world consumption.We present the first data on Sc speciation in lateritic deposits by combining quantitative mineralogy, geochemical analysis and X-ray absorption near-edge structure (XANES) spectroscopy on drill-core samples from the lateritic profile of the Syerston-Flemington deposit. The results explain the geochemical conditions required to form such exceptional Sc concentrations and improve our understanding of the geochemical behaviour of this under-explored element. Geological ContextIn Eastern Australia, lateritic profiles developed under seasonally dry humid tropical climatic conditions that resulted in intensive weathering during the Tertiary; the present occurrences are often erosional remnants of fossil laterite (Milnes et al., 1987). The Syerston-Flemington deposit (Fig. 1a and Table S-1) is part of the lateritic cover developed over the Tout complex, an ultramafic-mafic 'Alaskan-type' intrusive complex in the Lachlan Fold Belt (Johan et al., 1989). Scandium anomalies have been found over a body of nearly pure clinopyroxenite (Fig. S-1), with Sc concentrations (ca. 80 ppm; Table S-3) twice as high as those in typical mantle clinopyroxenites (Samson and Chassé, 2016). Similar concentrations (60 ppm to 80 ppm) occur in other 'Alaskan-type' clinopyroxenites (Burg et al., 2009) and in clinopyroxenes from ocean-island basalts (Dorais, 2015). This suggests the accumulation of clinopyroxene in subvolcanic feeder conduits during fractional crystallisation of a mantle-derived melt. Anomalies of Sc concentration in the parent rock result from specific conditions of formation and are not shared by all ultramafic-mafic bedrocks. Scandium (Sc) has unique properties, highly valued for many applications. Future supply is expected to rely on unusually high-grade (up to 1000 ppm) lateritic Sc ores discovered in Eastern Australia. To understand the origin of such exceptional concentrations, we investigated Sc speciation in one of these d...

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Unsporting scandium

Cited by 29 publications

References 3 publications

Petrology and geochemistry of scandium in New Caledonian Ni-Co laterites

Petrology and geochemistry of scandium in New Caledonian Ni-Co laterites

Influence of crystallographic environment on scandium K-edge X-ray absorption near-edge structure spectra

Scandium speciation in a world-class lateritic deposit

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